Classifications

• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04W—WIRELESS COMMUNICATION NETWORKS
  • H04W36/00—Hand-off or reselection arrangements
  • H04W36/0005—Control or signalling for completing the hand-off
  • H04W36/0055—Transmission or use of information for re-establishing the radio link
  • H04W36/0061—Transmission or use of information for re-establishing the radio link of neighbour cell information
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04W—WIRELESS COMMUNICATION NETWORKS
  • H04W36/00—Hand-off or reselection arrangements
  • H04W36/0005—Control or signalling for completing the hand-off
  • H04W36/0055—Transmission or use of information for re-establishing the radio link
  • H04W36/0072—Transmission or use of information for re-establishing the radio link of resource information of target access point
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04W—WIRELESS COMMUNICATION NETWORKS
  • H04W36/00—Hand-off or reselection arrangements
  • H04W36/0005—Control or signalling for completing the hand-off
  • H04W36/0083—Determination of parameters used for hand-off, e.g. generation or modification of neighbour cell lists
  • H04W36/0085—Hand-off measurements
  • H04W36/0088—Scheduling hand-off measurements
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04W—WIRELESS COMMUNICATION NETWORKS
  • H04W36/00—Hand-off or reselection arrangements
  • H04W36/0005—Control or signalling for completing the hand-off
  • H04W36/0083—Determination of parameters used for hand-off, e.g. generation or modification of neighbour cell lists
  • H04W36/0085—Hand-off measurements
  • H04W36/0094—Definition of hand-off measurement parameters
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04W—WIRELESS COMMUNICATION NETWORKS
  • H04W36/00—Hand-off or reselection arrangements
  • H04W36/08—Reselecting an access point
  • H04W36/085—Reselecting an access point involving beams of access points
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04W—WIRELESS COMMUNICATION NETWORKS
  • H04W36/00—Hand-off or reselection arrangements
  • H04W36/24—Reselection being triggered by specific parameters
  • H04W36/30—Reselection being triggered by specific parameters by measured or perceived connection quality data
  • H04W36/302—Reselection being triggered by specific parameters by measured or perceived connection quality data due to low signal strength
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04W—WIRELESS COMMUNICATION NETWORKS
  • H04W36/00—Hand-off or reselection arrangements
  • H04W36/34—Reselection control
  • H04W36/38—Reselection control by fixed network equipment
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04W—WIRELESS COMMUNICATION NETWORKS
  • H04W72/00—Local resource management
  • H04W72/04—Wireless resource allocation
  • H04W72/044—Wireless resource allocation based on the type of the allocated resource
  • H04W72/0446—Resources in time domain, e.g. slots or frames
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04W—WIRELESS COMMUNICATION NETWORKS
  • H04W72/00—Local resource management
  • H04W72/04—Wireless resource allocation
  • H04W72/044—Wireless resource allocation based on the type of the allocated resource
  • H04W72/046—Wireless resource allocation based on the type of the allocated resource the resource being in the space domain, e.g. beams

Definitions

• the present disclosure generally relates to the technical field of wireless communications, and particularly, to a network device, a terminal device and methods respectively implemented in the network device and the terminal device for facilitating handover of the terminal device served by the network device to a target beam and/or network device.
• the radio coverage area offered by a network device in high-frequency wireless communication systems would be much smaller than in existing low-frequency systems. Together with the limited ability for the radio waves at the concerned frequencies to diffract, this makes sudden loss of coverage of its serving network device a potentially much more frequent event to a moving terminal device.
• a terminal device has to be handed over to a new beam and/or network device when its current serving beam can no longer provide the coverage it needs, and the terminal device can only know which beam and/or network device to connect to and how to connect to the target beam and/or network device during a handover procedure via a HO command received from its serving network device.
• Such a HO command is a bit large in size as it includes all necessary information to tell the terminal device how to connect to a target beam and/or network device (hereinafter referred to as information on configuration for the target beam and/or network device) . Accordingly, the transmission of the HO command is relatively time consuming and not easy to protect (for example, through the use of Forward Error Correction (FEC) encoding) . Moreover, because the HO command is vulnerable to transmission error as explained above, there is a higher risk that the terminal device does not successfully receive the HO command from its serving network device and thus cannot know which beam and/or network device to connect to and how to connect thereto. Accordingly, it has to detect a new network device from scratch and the overall recover procedure takes a relatively long time.
• FEC Forward Error Correction
• embodiments of the present disclosure provide solutions for facilitating handover of a terminal device served by a network device to a target beam and/or network device.
• a method in a network device for facilitating handover of a terminal device served by the network device to a target beam and/or network device.
• the method includes transmitting information on configurations for a set of candidate target beams and/or network devices to the terminal device before the handover of the terminal device is triggered.
• the method further includes transmitting a handover command to the terminal device to trigger the handover of the terminal device.
• the handover command contains an identifier for identifying, from the transmitted information on the configurations for the candidate target beams and/or network devices, the information on the configuration for the target beam and/or network device.
• the proposed solution information on configurations for all candidate target beams and/or network devices is transmitted to the terminal device indicating how to connect to the respective candidate target beams and/or network devices, before a handover command containing an identifier is transmitted to the terminal device identifying, from the transmitted configuration information, the specific part for the actual target beam and/or network device of the terminal device.
• the information on the configuration for the actual target beam and/or network device can be omitted from the HO command.
• the HO command is significantly reduced in size as compared with the existing HO command which contains not only an identifier of but also detailed configuration information for the actual target beam and/or network device of the terminal device as described above.
• the transmission of the configuration information for the actual target beam and/or network device as well as other candidate target beam and/or network device is reliable, as it occurs when there is a good connection between the terminal device and its serving network device and the handover of the terminal device is not triggered yet.
• the information on the configurations for the candidate target beams and/or network devices may be stored in a table with indexes each uniquely identifying, from the table, an entry containing information on a respective one of the configurations for the candidate target beams and/or network devices.
• the identifier for identifying the information on the configuration for the target beam and/or network device may be one of the indexes which identifies an entry containing the information on the configuration for the target beam and/or network device.
• the indexes may be generated from identifiers of the candidate target beams and/or network devices, respectively.
• the set of candidate target beams and/or network devices may include some or all of neighboring beams and/or network devices of the terminal device’s serving beam and/or network device.
• the information on the configurations for the set of candidate target beams and/or network devices may be transmitted to the terminal device immediately after the terminal device connects to its serving beam and/or network device.
• the information on the configurations for the set of candidate target beams and/or network devices may be transmitted to the terminal device when communication quality between the terminal device and its serving beam and/or network device falls down below a threshold.
• the method may further include stopping Mobile Reference Signal (MRS) transmissions from the serving network device and from all the set of candidate target beams and/or network devices except the target beam and/or network device after the handover command is transmitted and requiring only the target beam and/or network device to transmit a MRS for a predetermined time period after the handover command is transmitted, so that the identifier for identifying the information on the configuration for the target beam and/or network device is derivable at the terminal device from the MRS transmitted via the target beam and/or network device and received by the terminal device.
• MRS Mobile Reference Signal
• a method in a terminal device for facilitating handover of the terminal device served by its serving network device to a target beam and/or network device.
• the method includes receiving information on configurations for a set of candidate target beams and/or network devices from the serving network device before the handover of the terminal device is triggered.
• the method further includes identifying, from the received information on the configurations for the candidate target beams and/or network devices, information on a configuration for the target beam and/or network device, based on a received or derived identifier for the information on the configuration for the target beam and/or network device.
• the method may further include receiving from the serving network device a handover command that triggers the handover of the terminal device, wherein the handover command contains the identifier for the information on the configuration for the target beam and/or network device.
• the method may further include receiving a MRS from the target beam and/or network device for a predetermined time period while no MRS is received from the serving beam and/or network device or other candidate target beams and/or network devices among the set of candidate target beams and/or network devices during the time period. Then, the identifier for the information on the configuration for the target beam and/or network device is derived from the MRS received from the target beam and/or network device.
• a network device for facilitating handover of a terminal device served by the network device to a target beam and/or network device.
• the network device includes a generating unit and a transceiving unit.
• the generating unit is configured to generate information on configurations for a set of candidate target beams and/or network devices transmitted to the terminal device before the handover of the terminal device is triggered.
• the generating unit is further configured to generate a handover command transmitted to the terminal device to trigger the handover of the terminal device.
• the handover command contains an identifier for identifying, from the transmitted information on the configurations for the candidate target beams and/or network devices, the information on the configuration for the target beam and/or network device.
• the transceiving unit is configured to transmit the information on configurations for the set of candidate target beams and/or network devices and the handover command to the terminal device.
• a terminal device for facilitating handover of the terminal device served by its serving network device to a target beam and/or network device.
• the terminal device includes a transceiving unit and an identifying unit.
• the transceiving unit is configured to receive information on configurations for a set of candidate target beams and/or network devices from the serving network device before the handover of the terminal device is triggered.
• the identifying unit is configured to identify, from the received information on the configurations for the candidate target beams and/or network devices, information on a configuration for the target beam and/or network device, based on a received or derived identifier for the information on the configuration for the target beam and/or network device.
• the transceiving unit may be further configured to receive from the serving network device a handover command that triggers the handover of the terminal device, wherein the handover command contains the identifier for the information on the configuration for the target beam and/or network device.
• the transceiving unit may be further configured to receive a MRS from the target beam and/or network device for a predetermined time period while no MRS is received from the serving beam and/or network device or other candidate target beams and/or network devices among the set of candidate target beams and/or network devices during the time period.
• the terminal device may further include a deriving unit configured to derive the identifier for the information on the configuration for the target beam and/or network device from the MRS received from the target beam and/or network device.
• a network device for facilitating handover of a terminal device served by the network device to a target beam and/or network device.
• the network device includes a memory and a processor.
• the memory has machine-readable instructions stored therein.
• the processor executes the stored machine-readable instructions to control the network device to perform the method according to the first aspect of the present disclosure.
• a terminal device for facilitating handover of the terminal device served by its serving network device to a target beam and/or network device.
• the terminal device includes a method and a processor.
• the memory has machine-readable instructions stored therein.
• the processor executes the stored machine-readable instructions to control the terminal device to perform the method according to the second aspect of the present disclosure.
• a computer program product including a non-transitory computer readable storage medium storing therein executable instructions configured to implement a method according to the first aspect or the second aspect of the disclosure.
• a method performed in a wireless communication network for facilitating handover of a terminal device served by its serving network device to a target beam and/or network device.
• the method includes initiating, by a handover control unit, transmission of a handover command to the terminal device to trigger the handover of the terminal device.
• Information on configurations for a set of candidate target beams and/or network devices have been transmitted to the terminal device before the handover of the terminal device is triggered.
• the handover command contains an identifier for identifying, from the transmitted information on the configurations for the candidate target beams and/or network devices, the information on the configuration for the target beam and/or network device.
• Fig. 1 is a diagram illustrating a first handover scenario where a terminal device is handed over between beams from the same network device;
• Fig. 2 is a diagram illustrating a second handover scenario where a terminal device is handed over between beams from different network devices;
• Fig. 3 is a diagram illustrating a third handover scenario where a terminal device is handed over between different network devices each performing transmission in an omnidirectional manner;
• Fig. 4 is a flowchart illustrating a method implemented in a network device for facilitating handover of a terminal device served by a network device to a target beam and/or network device according to the present disclosure
• Figs. 5-7 are flowcharts illustrating a method implemented in a terminal device for facilitating handover of a terminal device served by a network device to a target beam and/or network device according to the present disclosure
• Fig. 8 is a diagram schematically an example of how a terminal device and its serving network device cooperate with each other to facilitate handover of the terminal device according to the present disclosure
• Fig. 9 is a block diagram illustrating an exemplary functional structure of a network device according to the present disclosure.
• Fig. 10 is a block diagram illustrating an exemplary software-based implementation of a network device according to the present disclosure
• Fig. 11 is a block diagram illustrating an exemplary functional structure of a terminal device according to the present disclosure.
• Fig. 12 is a block diagram illustrating an exemplary software-based implementation of a terminal device according to the present disclosure
• Fig. 13 is a schematic diagram illustrating an exemplary implementation wherein functions of the network device described in conjunction with Figs. 9 and 10 are performed by a single network device within a wireless network;
• Fig. 14 is a schematic diagram illustrating an alternative implementation wherein functions of the network device described in conjunction with Figs. 9 and 10 are distributed over two network devices within a wireless network.
• a terminal device refers to any end device that can access a wireless communication network and receive services therefrom.
• a terminal device may be a user equipment (UE) , which may be a Subscriber Station (SS) , a Portable Subscriber Station, a Mobile Station (MS) , or an Access Terminal (AT) .
• the mobile terminal may include, but is not limited to, a mobile phone, a cellular phone, a smart phone, a tablet, a wearable device, a personal digital assistant (PDA) , and the like.
• PDA personal digital assistant
• network device refers to a device at the network side and may include a network device via which a terminal device accesses the network and receives services therefrom.
• a network device may be a base station (BS) , a node B (NodeB or NB) , an evolved NodeB (eNodeB or eNB) , a Remote Radio Unit (RRU) , a radio header (RH) , a remote radio head (RRH) , a relay, a low power node such as a femto, a pico, and so forth.
• BS base station
• NodeB or NB node B
• eNodeB or eNB evolved NodeB
• RRU Remote Radio Unit
• RH radio header
• RRH remote radio head
• relay a low power node such as a femto, a pico, and so forth.
• first and second refer to different elements.
• the singular forms “a” and “an” are intended to include the plural forms as well, unless the context clearly indicates otherwise.
• the term “based on” is to be read as “based at least in part on. ”
• the term “one embodiment” and “an embodiment” are to be read as “at least one embodiment. ”
• the term “another embodiment” is to be read as “at least one other embodiment. ”
• Other definitions, explicit and implicit, may be included below.
• Some or all of the functions described may be implemented using hardware circuitry, such as analog and/or discrete logic gates interconnected to perform a specialized function, Application Specific Integrated Circuits (ASICs) , Programmable Logical Arrays (PLAs) , etc. Likewise, some or all of the functions may be implemented using software programs and data in conjunction with one or more digital microprocessors or general purpose computers. Where nodes that communicate using the air interface are described, it will be appreciated that those nodes also have suitable radio communications circuitry.
• the technology can additionally be considered to be embodied entirely within any form of computer-readable memory, including non-transitory embodiments such as solid-state memory, magnetic disk, or optical disk containing an appropriate set of computer instructions that would cause a processor to carry out the techniques described herein.
• Hardware implementations of the presently disclosed techniques may include or encompass, without limitation, digital signal processor (DSP) hardware, a reduced instruction set processor, hardware (e.g., digital or analog) circuitry including but not limited to application specific integrated circuit (s) (ASIC) and/or field programmable gate array (s) (FPGA (s) ) , and (where appropriate) state machines capable of performing such functions.
• DSP digital signal processor
• ASIC application specific integrated circuit
• FPGA field programmable gate array
• a computer is generally understood to comprise one or more processors or one or more controllers, and the terms computer, processor, and controller may be employed interchangeably.
• the functions may be provided by a single dedicated computer or processor or controller, by a single shared computer or processor or controller, or by a plurality of individual computers or processors or controllers, some of which may be shared or distributed.
• the term “processor” or “controller” also refers to other hardware capable of performing such functions and/or executing software, such as the example hardware recited above.
• solutions proposed here may or may not be used together with beamforming.
• the proposed solutions are applicable to a first handover scenario where the handover of a terminal device occurs between beams from the same network device or a second handover scenario where the handover of a terminal device occurs between beams from different network devices.
• the proposed solutions are applicable to a third handover scenario where the handover of a terminal device occurs between different network devices.
• Fig. 1 depicts the first handover scenario, where beams 210 and 220 are transmitted from a network device 110 and a terminal device 300 is handed over from beam 210 to beam 220 as it moves from the coverage area of beam 210 to the coverage area of beam 220.
• Fig. 2 depicts the second handover scenario, where a beam 210 and a beam 220 are respectively transmitted from a network device 110 and a network device 120 and a terminal device 300 is handed over from beam 210 to beam 220 as it moves from the coverage area of beam 210 and hence network device 110 to the coverage area of beam 220 and hence network device 120.
• Fig. 1 depicts the first handover scenario, where beams 210 and 220 are transmitted from a network device 110 and a terminal device 300 is handed over from beam 210 to beam 220 as it moves from the coverage area of beam 210 to the coverage area of beam 220.
• Fig. 2 depicts the second handover scenario, where a beam 210 and a beam 220 are respectively transmitted from a network device
• FIG 3 depicts the third handover scenario, where a network device 110 and a network device 120 each serve a coverage area in an omnidirectional manner and a terminal device 300 is handed over from network device 110 to network device 120 as it moves from the coverage area of network device 110 to the coverage area of network device 120.
• Fig. 4 schematically illustrates a method 400 in a network device 110 for facilitating handover of a terminal device 300 served by the network device 110 to a target beam 220 and/or network device 120 according to the present disclosure.
• the method begins with block s410, at which information on configurations for a set of candidate target beams and/or network devices is transmitted to the terminal device 300 before the handover of the terminal device 300 is triggered.
• a configuration for a candidate target beam and/or network device specifies how to connect to the candidate target beam and/or network device, and needs to be known to the terminal device 300 for handover to the candidate target beam and/or network device.
• a configuration may include but is not limited to random access related configuration, such as at which time and frequency to send a Physical Random Access Channel (PRACH) preamble, how to receive a Radio Access Response (RAR) from the network, is the RAR accompanied with a control channel or not, or blind detection is needed to decode RAR, where is the Reference Signal (RS) located for RAR, what is the RS to be used for UE to transmit message 3.
• PRACH Physical Random Access Channel
• RAR Radio Access Response
• RS Reference Signal
• the set of candidate target beams and/or network devices may include all neighboring beams and/or network devices of the terminal device’s serving beam 210 and/or network device 110.
• the neighboring beams and/or network devices may be configured by Operation and Maintenance (O&M) , for example.
• the set of candidate target beams and/or network devices may include some of all the neighboring beams and/or network devices of the terminal device’s serving beam 210 and/or network device 110.
• the neighboring beams and/or network devices included in the set of candidate target beams and/or network devices may be selected from all the neighboring beams and/or network devices according to a predicted moving track of the terminal device.
• the terminal device may be mounted on a bus which sticks to a predetermined schedule and moves along a fixed route. In that case, the neighboring beams and/or network devices included in the set of candidate target beams and/or network devices may be selected as those along the route.
• the beams and/or network devices included in the set of candidate target beams and/or network devices may be selected from all the neighboring beams and/or network devices according to habits of the user of the terminal device and/or monitored qualities of the neighboring beams and/or network devices.
• the terminal device may be used by a person who is used to taking exercises in a park every morning.
• the neighboring beams and/or network devices included in the set of candidate target beams and/or network devices may be selected as those having coverage areas within or overlapping the area of the park.
• the neighboring beams and/or network devices included in the set of candidate target beams and/or network devices may be selected as those whose qualities are better than a threshold.
• the serving network device 110 can selectively transmit the information on configurations for the set of candidate target beams and network devices, the information on configurations for the set of candidate target beams or the information on configurations for the set of candidate target network devices to the terminal device 300 at block 410.
• the serving network device 300 determines that it supports beamforming and that the terminal device is far from the edge of its coverage area, then it can predict the specific handover scenario as the first handover scenario described above. In that case, the serving network device 300 only needs to transmit the information on configurations for the set of candidate target beams to the terminal device 300 at block s410.
• the serving network device 300 determines that its neighboring network devices and itself support beamforming and that the terminal device is near the edge of its coverage area, then it can predict the specific handover scenario as the second handover scenario described above. In that case, the serving network device 300 has to transmit the information on configurations for the set of candidate target beams and network devices to the terminal device 300.
• the serving network device 300 determines that its neighboring network devices and itself do not support beamforming and that the terminal device is near the edge of its coverage area, then it can predict the specific handover scenario as the third handover scenario described above. In that case, the serving network device only needs to transmit the information on configurations for the set of candidate target beams to the terminal device 300.
• the information on the configurations for the set of candidate target beams and/or network devices may be transmitted to the terminal device 300 immediately after the terminal device connects to its serving beam 210 and/or network device 110.
• the information on the configurations for the set of candidate target beams and/or network devices may be transmitted to the terminal device 300 when communication quality between the terminal device and its serving beam 210 and/or network device 110 falls down below a threshold (denoted as T1 ) .
• T1 a threshold
• Supposing the handover of the terminal device is triggered when the communication quality between the terminal device and its serving beam 210 and/or network device 110 falls down below a threshold (denoted as T2) , T1 should be higher than T2.
• a handover command is transmitted to the terminal device 300 at block s420 to trigger the handover of the terminal device 300.
• the handover command contains an identifier for identifying, from the transmitted information on the configurations for the candidate target beams and/or network devices, the information on the configuration for the target beam 220 and/or network device 120.
• the identifier of the target beam 220 and/or network device 120 may be used as the identifier contained in the handover command.
• the information on the configurations for the candidate target beams and/or network devices may be stored in a table with indexes each uniquely identifying, from the table, an entry containing information on a respective one of the configurations for the candidate target beams and/or network devices.
• the identifier for identifying the information on the configuration for the target beam 220 and/or network device 120 may be one of the indexes which identifies an entry containing the information on the configuration for the target beam 220 and/or network device 120.
• a table refers to a two-dimensional data structure that stores data elements in rows and columns.
• the configuration for each candidate target beam and/or network device may be stored in a respective row of the table, and the values of the same item (for example, at which time and frequency to send a Physical Random Access Channel (PRACH) preamble) of the configurations for the candidate target beams and/or network devices may be stored in a respective column of the table.
• PRACH Physical Random Access Channel
• the indexes may be generated from identifiers of the candidate target beams and/or network devices, respectively.
• any other data structure may be used instead of a table, as long as it can carry the configuration information for all candidate target beams and/or network devices.
• information on configurations for all candidate target beams and/or network devices is transmitted to the terminal device indicating how to connect to the respective candidate target beams and/or network devices, before a handover command containing an identifier is transmitted to the terminal device identifying, from the transmitted configuration information, the specific part for the actual target beam and/or network device of the terminal device.
• the information on the configuration for the actual target beam and/or network device can be omitted from the HO command. Accordingly, the HO command is significantly reduced in size as compared with the prior art HO command which contains not only an identifier of but also detailed configuration information for the actual target beam and/or network device of the terminal device. Accordingly, the HO command can be transmitted in a shorter time period with higher reliability.
• the transmission of the configuration information for the actual target beam and/or network device as well as other candidate target beam and/or network device is reliable, as it occurs when there is a good connection between the terminal device and its serving network device and the handover of the terminal device is not triggered yet.
• the method 400 may further comprise block s430 shown in dashed block in Fig. 4.
• the serving network device 110 stops Mobile Reference Signal (MRS) transmissions from the serving network device 110 and from all the set of candidate target beams and/or network devices except the target beam 220 and/or network device 120 after the handover command is transmitted and requires only the target beam and/or network device to transmit a MRS for a predetermined time period after the handover command is transmitted, so that the identifier for identifying the information on the configuration for the target beam 220 and/or network device 120 is derivable at the terminal device from the MRS transmitted via the target beam and/or network device and received by the terminal device.
• MRS Mobile Reference Signal
• the terminal device 300 can derive from the received MRS an identifier for identifying, from the received configuration information for all candidate target beams and/or network devices, the specific part for the actual target beam 220 and/or network device 120. As a result, the risk of handover failure is reduced.
• the present disclosure provides a method 500 implemented in the terminal device for facilitating handover of the terminal device to a target beam and/or network device.
• the method 500 begins with block s510, at which information on configurations for a set of candidate target beams and/or network devices is received from the serving network device 110 before the handover of the terminal device 300 is triggered.
• block s510 information on a configuration for the target beam 220 and/or network device 120 is identified at block s550 from the received information on the configurations for the candidate target beams and/or network devices, based on a received or derived identifier for the information on the configuration for the target beam 220 and/or network device 120.
• the method 500 may further comprise block s520 as illustrated in Fig. 6.
• the terminal device 300 receives from the serving network device 110 a handover command that triggers the handover of the terminal device 300.
• the handover command contains the identifier for the information on the configuration for the target beam 220 and/or network device 120.
• the method 500 may further comprise blocks s530 and s540 as illustrated in Fig. 7.
• the terminal device 300 receives a MRS from the target beam and/or network device for a predetermined time period while no MRS is received from the serving beam and/or network device or other candidate target beams and/or network devices among the set of candidate target beams and/or network devices during the time period.
• the terminal device 300 derives the identifier for the information on the configuration for the target beam 220 and/or network device 120 from the MRS received from the target beam and/or network device.
• FIG. 8 presents an example of how the serving network device 110 and the terminal device 300, which perform the above-described methods 400 and 500 respectively, cooperate with each other to facilitate handover of the terminal device 300.
• the example is described with respect to the above-described third handover scenario, where the network device 110 and the network device 120 each serve a coverage area in an omnidirectional manner and the terminal device 300 is handed over from network device 110 to network device 120 as it moves from the coverage area of network device 110 to the coverage area of network device 120.
• the serving network device 110 transmits information on configurations for a set of candidate target network devices to the terminal device 300.
• the set of candidate target network devices include all neighboring network devices of the terminal device’s serving network device 110, and the information on the configurations for the candidate network devices is stored in a table with indexes.
• the serving network device 10 Upon detecting that communication quality between the terminal device 300 and the serving network device 110 is lower than a threshold at step s820, the serving network device 10 transmits a handover command to the terminal device 300 at step s830.
• the handover command contains an identifier for identifying, from the transmitted information on the configurations for the candidate target network devices, the information on the configuration for the target network device 120.
• the identifier contained in the handover command may be one of the indexes which corresponds to the target network device 120.
• the serving network device 110 stops MRS transmission after the handover command is transmitted and requires only the target network device 120 among the set of candidate target network devices to transmit a MRS for a predetermined time period (denoted as t) after the handover command is transmitted, so that the identifier for identifying the information on the configuration for the target network device 120 is derivable at the terminal device 300 from the MRS transmitted via the target network device 120 and received by the terminal device 300.
• the terminal device 300 identifies, from the information on the configurations for the candidate target beams and/or network devices received at step s810, information on a configuration for the target network device 120, based on a received or derived identifier for the information on the configuration for the target network device 120. Finally, at step s860, the terminal device 300 connects to the target node 120 according to the identified information on a configuration for the target network device 120.
• the network device 110 includes a generating unit 1101 and a transceiving unit 1102.
• the generating unit 1101 is configured to generate information on configurations for a set of candidate target beams and/or network devices transmitted to the terminal device 300 before the handover of the terminal device 300 is triggered.
• the generating unit 1101 is further configured to generate a handover command transmitted to the terminal device 300 to trigger the handover of the terminal device 300.
• the handover command contains an identifier for identifying, from the transmitted information on the configurations for the candidate target beams and/or network devices, the information on the configuration for the target beam 220 and/or network device 120.
• the transceiving unit 1102 is configured to transmit the information on configurations for the set of candidate target beams and/or network devices and the handover command to the terminal device 300.
• the information on the configurations for the candidate target beams and/or network devices may be stored in a table with indexes each uniquely identifying, from the table, an entry containing information on a respective one of the configurations for the candidate target beams and/or network devices.
• the identifier for identifying the information on the configuration for the target beam 220 and/or network device 120 may be one of the indexes which identifies an entry containing the information on the configuration for the target beam 220 and/or network device 120.
• the indexes may be generated from identifiers of the candidate target beams and/or network devices, respectively.
• the set of candidate target beams and/or network devices may include all neighboring beams and/or network devices of the terminal device’s serving beam 210 and/or network device 110.
• the set of candidate target beams and/or network devices may include some neighboring beams and/or network devices of the terminal device’s serving beam 210 and/or network device 110, which are selected according to a predicted moving track of the terminal device.
• the information on the configurations for the set of candidate target beams and/or network devices may be transmitted to the terminal device 300 immediately after the terminal device connects to its serving beam 210 and/or network device 110.
• the information on the configurations for the set of candidate target beams and/or network devices may be transmitted to the terminal device 300 when communication quality between the terminal device and its serving beam 210 and/or network device 110 falls down below a threshold.
• the above-described units may be implemented separately as suitable dedicated circuits. Nevertheless, these units can also be implemented using any number of dedicated circuits through functional combination or separation. In some embodiments, these units may be even combined in a single application specific integrated circuit (ASIC) .
• ASIC application specific integrated circuit
• a network device 110 including a memory 1101’ and a processor 1102’ (including but not limited to a microprocessor, a microcontroller or a Digital Signal Processor (DSP) , etc. ) as illustrated in Fig. 10.
• the memory 1101’ stores machine-readable program code executable by the processor.
• the processor 1102’ when executing the machine-readable program code, controls the network device 110’ to perform the above-described method 400.
• the terminal device 300 includes a transceiving unit 3001 and an identifying unit 3002.
• the transceiving unit 3001 is configured to receive information on configurations for a set of candidate target beams and/or network devices from the serving network device 110 before the handover of the terminal device 300 is triggered.
• the identifying unit 3002 is configured to identify, from the received information on the configurations for the candidate target beams and/or network devices, information on a configuration for the target beam 220 and/or network device 120, based on a received or derived identifier for the information on the configuration for the target beam 220 and/or network device 120.
• the transceiving unit 3001 may be further configured to receive from the serving network device 110 a handover command that triggers the handover of the terminal device 300, wherein the handover command contains the identifier for the information on the configuration for the target beam 220 and/or network device 120.
• the transceiving unit 3001 may be further configured to receive a MRS from the target beam and/or network device for a predetermined time period while no MRS is received from the serving beam and/or network device or other candidate target beams and/or network devices among the set of candidate target beams and/or network devices during the time period.
• the terminal device 300 may further comprise a deriving unit 3003 configured to derive the identifier for the information on the configuration for the target beam 220 and/or network device 120 from the MRS received from the target beam and/or network device.
• the above-described units may be implemented separately as suitable dedicated circuits. Nevertheless, these units can also be implemented using any number of dedicated circuits through functional combination or separation. In some embodiments, these units may be even combined in a single application specific integrated circuit (ASlC) .
• ASlC application specific integrated circuit
• a terminal device 300 including a transceiver 3001’ , a processor 3002’ (including but not limited to a microprocessor, a microcontroller or a Digital Signal Processor (DSP) , etc. ) coupled to the transceiver 3001’ and a memory 3003’ as illustrated in Fig. 12.
• the transceiver 3001’ is for bidirectional wireless communications and has at least one antenna to facilitate communication.
• the memory 3003’ stores machine-readable program code executable by the processor 3002’ .
• the processor 3002’ when executing the machine-readable program code, controls the terminal device 300’ to perform the above-described method 500.
• Fig. 13 is a schematic diagram illustrating an exemplary implementation wherein functions of the network device 110/110’ described in conjunction with Figs. 9 and 10 are performed by a single network device 1300 within a wireless communication network.
• Network Device 1300 may, in some embodiments, be an electronic device being communicatively connected to other electronic devices on the network (e.g., other network devices, end-user devices, radio base stations, etc. ) .
• a network device may include radio access features that provide wireless radio network access to other electronic devices such as UEs.
• network device 1300 may be an eNodeB in Long Term Evolution (LTE) or other type of base station as well as a radio network controller.
• LTE Long Term Evolution
• Network device (ND) 1300 may store and transmit (internally and/or with other electronic devices over a network) code (which is composed of software instructions and which is sometimes referred to as computer program code or a computer program) and/or data using non-transitory machine-readable media (also called computer-readable media) , such as machine-readable storage media (e.g., magnetic disks, optical disks, read only memory (ROM) , flash memory devices, phase change memory) and machine-readable transmission media (also called a carrier) (e.g., electrical, optical, radio, acoustical or other form of propagated signals -such as carrier waves, infrared signals) .
• machine-readable storage media e.g., magnetic disks, optical disks, read only memory (ROM) , flash memory devices, phase change memory
• machine-readable transmission media also called a carrier
• carrier e.g., electrical, optical, radio, acoustical or other form of propagated signals -such as carrier waves, infrared signals
• network device 1300 includes a processor 1301, a memory 1302, an interface 1303 and an antenna 1304. These components may work together to provide various network device functionality as disclosed hereinabove. Such functionality may include implementing all, or a portion, of the modules depicted in Fig. 13.
• the components of the network device 1300 are depicted as single boxes located within a single larger box for reasons of simplicity in describing certain aspects and features disclosed herein.
• the network device 1300 may include multiple different physical components that make up a single illustrated component (e.g., the interface 1303 may comprise terminals for coupling wires for a wired connection and a radio transceiver for a wireless connection) .
• the network device 1300 may be a virtual network device in which multiple different physically separate components interact to provide the functionality of network device 1300 (e.g., processor 1301 may comprise three separate processors located in three separate enclosures, where each processor is responsible for a different function for a particular instance of radio access network device 1300) .
• network device 1300 may be composed of multiple physically separate components (e.g., a NodeB component and a Radio Network Controller (RNC) component, a Base Transceiver Station (BTS) component and a Base Station Controller (BSC) component, etc. ) , which may each have their own respective processor, storage, and interface components. These components may be dedicated components or they may be shared in a virtualized context. In certain scenarios in which network device 1300 includes multiple separate components (e.g., BTS and BSC components) , one or more of the separate components may be shared among several network devices.
• RNC Radio Network Controller
• BTS Base Transceiver Station
• BSC Base Station Controller
• a single RNC may control multiple NodeB’s .
• each unique NodeB and BSC pair may be a separate network device.
• network device 1300 may be configured such that some components may be duplicated (e.g., separate memory 1302 for different virtual instances) and some components may be reused (e.g., the same antenna 1304 may be shared by any and all virtual instances) .
• Processor 1301 may be a combination of one or more of a microprocessor, controller, microcontroller, central processing unit, digital signal processor, application specific integrated circuit, field programmable gate array, or any other suitable computing device, resource, or combination of hardware, software and/or encoded logic operable to provide, either alone or in conjunction with other network device 1300 components, such as memory 1302.
• Memory 1302 may comprise non-transitory machine readable storage media (also called computer-readable media) having stored therein software.
• memory 1302 may comprise non-volatile memory containing code to be executed by processor 1301. Because memory 1302 is non-volatile, the code and/or data stored therein can persist even when the network device is turned off (when power is removed) . In some instances, while the network device is turned on that part of the code that is to be executed by the processor (s) may be copied from non-volatile memory into volatile memory (e.g., dynamic random access memory (DRAM) , static random access memory (SRAM) ) of that network device.
• DRAM dynamic random access memory
• SRAM static random access memory
• Interface 1303 may be used in the wired or wireless communication of signaling and/or data to or from network device 1300.
• interface 1303 may perform any formatting, coding, or translating that may be needed to allow network device 1300 to send and receive data whether over a wired or a wireless connection.
• interface 1303 may be coupled to one or more antennas 1304 which may include one or more transceivers for communicating with other similar network devices, with end user equipment and with other network devices.
• interface 1303 may comprise radio circuitry that may receive digital data that is to be sent out to other network devices via a wireless connection. The radio circuitry may convert the digital data into a radio signal having the appropriate parameters (e.g., frequency, timing, channel, bandwidth, etc. ) . The radio signal may then be transmitted via antennas 1304 to the appropriate recipient (s) .
• the radio circuitry of interface 1303 may in some instances comprise functionality for linking the Common Public Radio Interface (CPRI) stream and the antenna 1304.
• CPRI Common Public Radio Interface
• the L1 module 1305 handles uplink and downlink in the physical layer, layer 1 of the protocol stack.
• the L1 module processes antenna data received from the radio circuitry (e.g., over Common Public Radio Interface (CPRI) ) , which data processing may include removing cyclic prefix, running Fast Fourier Transform (FFT) to extract sub-channels, decoding/demodulating symbols, extracting physical channels and passing user information up to the lower layer of L2 Media Access Control (MAC) .
• CPRI Common Public Radio Interface
• FFT Fast Fourier Transform
• MAC Media Access Control
• the L1 module takes user data provided by lower layer of L2 MAC.
• Examples of tasks that may be performed by the L1 module in downlink may include constructing physical channels, performing turbo coding, scrambling, modulating, layer mapping, pre-coding, frequency mapping, inverse FFT, and cyclic prefix insertion and sending antenna data (e.g., over CPRI) to the interface 1303.
• specialized hardware may be used, including accelerators, to form processing chains.
• the L2-Sync module 1306 includes the synchronous parts of layer 2 of the protocol stack.
• the L2-Sync module includes the 3rd Generation Partnership Project (3GPP) sub-layers Medium Access Control (MAC) (including Hybrid Automatic Repeat Request (HARQ) ) and Radio Link Control (RLC) .
• the MAC sub-layer may have a separate HARQ entity for each connected UE, and a few additional HARQ entities for common needs such as system information, paging, and random access response.
• the RLC sub-layer may have a separate RLC entity for each logical channel, corresponding to radio bearers. Downlink and uplink may operate independently of each other, with some signaling forwarded from the uplink to the downlink.
• a task of the L2-Sync module in downlink may be to take Packet Data Convergence Protocol (PDCP) Packet Data Units (PDUs) from a PDCP PDU buffer and build MAC PDUs that are sent to the L1 module. This may be triggered by a transmit order from User Plane Control (UPC) module.
• the L2-Sync module may also handle multiplexing of logical channels, HARQ retransmissions, MAC control elements, MAC procedures such as random access, RLC PDU buffering and retransmissions, and RLC status messages.
• the PDCP PDU buffers may typically be shared between the L2-Async module and the L2-Sync module.
• a flow control mechanism may be added to transfer PDCP PDUs from the L2-Async module to the L2-Sync module.
• a task of the L2-Sync module in uplink may be to deconstruct MAC PDUs received from the L1 module into PDCP PDUs that are delivered to the L2-Async module.
• the L2-Sync module may also handle MAC control elements, MAC procedures such as random access, demultiplexing of logical channels, RLC PDU buffering, reordering and retransmissions, and RLC status messages.
• the L2-Sync module may not be part of a latency critical processing path, but may have a direct impact on the end-to-end packet latency.
• the UPC (User Plane Control) module 1307 includes fast radio resource management (RRM) functions that may occur on a per-subframe basis. This may include air-interface resource scheduling, link adaptation (transport format selection) , and power control.
• the UPC module may use input from other modules such as the L1 module and the L2-Sync module, and generate messages to other modules such as the L1 module and the L2-Sync module.
• the input may include buffer status reports, measurement reports, Channel Quality Indicator (CQI) reports, and HARQ feedback.
• the messages may be control information sent to the UEs, as well as uplink and downlink scheduling commands sent to the L1 module and the L2-Sync module.
• the UPC module may thus handle scheduling and optimization problems, involving many UEs and shared resources such as spectrum, power, and hardware.
• the L2-Async module 1308 includes the PDCP layer, whose primary tasks may be ciphering, header compression, and integrity protection for signaling. It may also support Iossless handover. In downlink, L2-Async module may maintain a PDCP PDU buffer, which is often shared with the L2-Sync module when suitable, as discussed above.
• the RRM-C (Radio Resource Management Coordination) module 1309 includes functions to coordinate multiple UPC instances.
• the RRM-C module may include functions for performing one or more of the following: Coordinated MultiPoint (CoMP) including fast and slow uplink/downlink, Combined Cell, Dual Connectivity, Inter-Cell Interference Coordination (ICIC) , enhanced Inter-Cell Interference Coordination (elCIC) and Further enhanced Inter-Cell Interference Coordination (FelCIC) .
• CoMP Coordinated MultiPoint
• ICIC Inter-Cell Interference Coordination
• elCIC enhanced Inter-Cell Interference Coordination
• FelCIC Further enhanced Inter-Cell Interference Coordination
• the RRM-C module may take input from the L1 and the L2-Async modules and generate messages to the UPC module.
• the UEH (User Equipment Handler) module 1310 includes functions for the handling and control of UE related control plane functions.
• UEH consists of 3GPP sub-layer Radio Resource Control (RRC) . This includes the control of one or more of the following functions: Connection handling, such as setup and release of connections; Mobility handling, such as handover or redirection release; UE Measurement Control; Load Management, such as Inter-Frequency Load Balancing and Offload; and Enhanced Multimedia Broadcast and Multicast Services (eMBMS) .
• RRC Radio Resource Control
• Connection handling such as setup and release of connections
• Mobility handling such as handover or redirection release
• UE Measurement Control UE Measurement Control
• Load Management such as Inter-Frequency Load Balancing and Offload
• eMBMS Enhanced Multimedia Broadcast and Multicast Services
• the UEH module may logically have a separate entity for each connected UE, storing all necessary data in a UE Context. Each separate entity may also implement the state machine for running all control-plane features related to a UE, including the necessary coordination between different functions for a specific UE.
• the RNH (Radio Network Handler) module 1311 includes functionality to manage logical cells in the radio network on order from an operator.
• the RNH module may also be responsible for the handling of LRAT specific configuration data on cell and node/device level. This also includes the handling of cell relations and neighbor cell data, such as Evolved Universal Terrestrial Radio Access Network (EUTRAN) neighbor cells and cells belonging to other RATs.
• the RNH module may also implement a number of Self-Organizing Network (SON) related functions such as automatic handling of neighbor relations (ANR) ; X2 Handling, i.e. automatic handling of external base station and cells references received from another base station over an interface used for communication between base stations, such as X2; and Mobility Robustness Optimization (MRO) , i.e. automatic tuning of mobility related parameters.
• ANR automatic handling of neighbor relations
• X2 Handling i.e. automatic handling of external base station and cells references received from another base station over an interface used for communication between base stations, such as X2
• the TN (Transport Network) module 1312 includes features for providing the node/device with transport network capabilities based on Internet Protocol (IP) (both IPv4 and IPv6 hosts) for messages with forwarding and protocol termination.
• IP Internet Protocol
• protocols could include Stream Control Transmission Protocol (SCTP) , Transmission Control Protocol (TCP) , User Datagram Protocol (UDP) and GPRS Tunneling Protocol User Plane, (GTP-U) , with support for Security, the protocols to be used over the paths S1, M3, X2 and/or Mul.
• the TN module may handle the forwarding of TN traffic between Digital Units (DUs) (within the node/device and between node/devices) and management of Site Local Area Networks (LAN) packets forwarding to the Operations and Maintenance (OAM) system.
• Security may be supported with Internet Protocol Security (IPSec) , including Internet Key Exchange (IKE) handling and Access control lists (ACL) for the Site LAN.
• IPSec Internet Protocol Security
• IKE Internet Key Exchange
• ACL Access control lists
• the TN module may also handle shaping capabilities for overload situations on the transport network when needed. The interaction between the transport and radio network makes it possible for the radio domain to adapt to the actual resource situation in the backhaul network.
• This can be the available S1 path (s) in the transport network to the core network or X2 path (s) to neighboring cell sites.
• functions of the network device 110/110’ described in conjunction with Figs. 9 and 10 may be distributed over two network devices within a wireless communication network as illustrated in Fig. 14.
• another network device 1500 separate from the network device 1400 also implements an UEH module 1510 that cooperates with the UEH module 1410 in the network device 1400 for controlling handover.
• the network device 1400 may be a serving network device with which a terminal device may communicate directly so as to access the network and the network device 1500 may not communicate with the terminal device directly but serves as a handover control unit which initiates transmission of a handover command from the network device 1400 to the terminal device to trigger the handover of the terminal device.
• Information on configurations for a set of candidate target beams and/or network devices have been transmitted from the network device 1400 to the terminal device before the handover of the terminal device is triggered.
• the handover command contains an identifier for identifying, from the transmitted information on the configurations for the candidate target beams and/or network devices, the information on the configuration for the target beam and/or network device.
• the network device 1500 which serves as the handover control unit further stops Mobile Reference Signal (MRS) transmissions from the serving network device and from all the set of candidate target beams and/or network devices except the target beam and/or network device after the handover command is transmitted and requires only the target beam and/or network device among the set of candidate target beams and/or network devices to transmit a MRS for a predetermined time period after the handover command is transmitted, so that the identifier for identifying the information on the configuration for the target beam and/or network device is derivable at the terminal device from the MRS transmitted via the target beam and/or network device and received by the terminal device.
• MRS Mobile Reference Signal

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